This invention relates generally to anionic polymerization of 1,3-pentadiene (piperylene). The 1,3-pentadiene is generally in admixture with other saturated and unsaturated hydrocarbons containing 5 carbon atoms. One source of such an admixture is a 5-carbon distillation cut obtained from a cracking of petroleum. This invention also relates to polymers of 1,3-pentadiene so prepared. This invention further relates to hydrogenated polymers of 1,3-pentadiene.
First, anionic polymerization of conjugated dienes is known. Second, several anionic polymerization catalysts or initiators are known. Third, chain transfer agents and/or polar solvents have been used in some anionic polymerizations. Fourth, conjugated dienes in general, and linear conjugated dienes having 4 to 6 carbon atoms per molecule in particular, are generally thought to be equally suitable for purposes of the aforementioned references. Fifth, a pure or substantially pure diolefin feed stream is preferred. Other than those references which teach copolymerization of a conjugated diene with either another conjugated diolefin or a vinyl compound, only U.S. Pat. No. 3,505,304 to Davison et al. discloses preparation of polymers from an impure hydrocarbon fraction. Polymers so produced are generally rubbery polymers. Sixth, polymers prepared in accordance with the foregoing references may, depending upon the polymerization components and conditions, range from liquid polymers to solid polymers with a variety of molecular weights and molecular weight distributions.
In copending Application Ser. No. 455,146, filed Jan. 3, 1983, and now abandoned, is taught that 1,3-pentadiene is selectively polymerized from a mixture of saturated and unsaturated hydrocarbon compounds. The compounds have primarily 5 carbon atoms per molecule. Polymerization is effected by using an anionic polymerization initiator in conjunction with a polar solvent. Active hydrogen compounds and polymerization-terminating compounds may be inactivated and separated from the mixture of hydrocarbon compounds before starting polymerization. As an alternative, inactivation and separation of active hydrogen compounds and polymerization-terminating compounds may be omitted provided the anionic polymerization initiator is employed in an amount to (a) inactivate such compounds and (b) initiate polymerization of 1,3-pentadiene.